1. Field of the Invention
The present invention relates to a magnetic disk device including a rotatable magnetic disk, a rotatable carriage having a magnetic head attached to its end and a rotary actuator for rotating the carriage between a base and a cover.
2. Background and Related Art
Generally, the magnetic disk device as described above has been provided with a voice coil motor as a rotary actuator. The voice coil motor is equipped with a coil attached to a carriage and upper and lower yokes having magnets for applying a magnetic field to the coil.
Conventionally, an attaching part for attaching yokes for such a voice coil motor has been constructed as illustrated in FIG. 8. Referring to FIG. 8, reference numeral 1 designates a base, 2 designates a cover and a carriage (not illustrated) having a magnetic head attached to its end is provided so as to be rotatable about an axis O. Reference numeral 3 denotes a first lower yoke to which a first magnet 4 is attached, 5 designates a second upper yoke to which a second magnet 6 is attached and a coil (not shown) mounted on the carriage is located between the opposed surfaces of these magnets 4 and 6. The coil, the yokes 3 and 5 and the magnets 4 and 6 constitute the voice coil motor as the rotary actuator. The yokes 3 and 5 are connected together as one connected member, and then, the connected member is fixed to the base 1 by means of a fixing screw 7. The fixing screw 7 passes through the lower yoke 3 from the upper yoke 5 and is screwed to the base 1. After the yokes 3 and 5 are secured to the base 1 by means of the fixing screw 7, the cover 2 is mounted on them.
However, since the yokes 3 and 5 are only fixed to the base 1 by means of the fixing screw 7, it has been difficult to firmly secure them to the base. Further, when the carriage is rotated by the voice coil motor, the yokes 3 and 5 are vibrated thereby causing undesirable noise.
In addition, since the fixing screw 7 is located between the opposed surfaces of the yokes 3 and 5, the fixing screw 7 may become an obstacle when the carriage is mounted between the base and the cover. When the carriage and the magnetic disk are mounted between the base and the cover, the carriage needs to be mounted between the opposed surfaces of the yokes 3 and 5 while being largely separated from the magnetic disk in order to prevent the carriage from interfering with the magnetic disk. The fixing screw 7 located between the opposed surfaces of the yokes 3 and 5 disadvantageously restricts the mounting position of the carriage. Therefore, the position of the fixing screw 7 must be set outward such that the fixing screw 7 does not interfere with the carriage in its mounted position. As a result, the size of yokes 3 and has needed to be enlarged, which resulted in enlarging the size of the entire body of the magnetic disk device.
Accordingly, it is an object of the present invention to provide a magnetic disk device in which the generation of vibration or noise can be prevented by firmly fixing the yokes of a rotary actuator and the size of the yokes can be reduced.
It is another object of the present invention to provide a magnetic disk device in which the movable range of the rotary actuator can be set wide.